The present invention relates to a plate-shaped constructional element made of wood, synthetic material or gypsum plaster boards in accordance with claim 1.
From the German Patent DE 43 15 759 or the European Patent EP 699 257 (corresponding U.S. Pat. No. 5,700,527) a sound absorbing constructional element made of glass or transparent synthetic glass is known which when mounted as facing shell at a spacing from a window, facade or roof structure element absorbs sound in a frequency range determined by the geometric dimensions of the spacing, the thickness of the facing shell, the size and the number of the holes in the micro-perforation as well as by the material of the facing shell. In further embodiments the same plate with micro-perforations may also be designed as closed cassette absorbing on one side or as flat or wing absorbing on both sides, which may have any shape whatsoever and present micro-perforations in one or several layers.
From the German Patent DE 44 37 196 moreover a sound absorber according to DE 43 15 759 is known wherein two plates having large holes are superimposed on top of each other such that small holes form a micro-perforation between the two plates. That invention is already based on the idea to compose micro-perforated structural elements of any materials whatsoever which resist micro-perforation by drilling, lasering or punching. By filling fine-grained spacing materials into the space between the coarsely perforated plates or by displacement of the immediately superimposed coarsely perforated plates it is equally possible to vary the micro-perforation within wide limits.
The German Patent De 43 12 885 (corresponding U.S. Pat. No. 5,740,649) equally discloses a sound-absorbing metal cassette as suspended false ceiling wherein one or several micro-perforated sheets disposed in spaced tandem arrangement extract the energy from the sound waves incident from the room side by the provision that the air in the holes as one mass together with the air between the sheets cooperates with the rough ceiling to form a complex mass spring system with inherent friction in the small holes.
Eventually, a sound absorber consisting of micro-perforated sheets or thin plates is known from the German Patent DE 197 54 107, wherein several sheets or plates are provided in any arrangement relative to each other and suspended from the ceiling of a room or in a horizontal or oblique position in the space. As in this case a compressible air cushion is deliberately dispensed with the small holes become here accessible for the sound waves from both sides of the sheets or thin plates and are hence able to develop their attenuating effect even without the stimulation by a resonance mechanism. Moreover, according to the German Patents DE 197 10 920 and 197 30 355 an effect of flow past or through the micro-perforated sheets or plates, which amplifies the sound absorption in the small holes, is expediently utilized.
Furthermore, gypsum plaster boards or wood boards or particle boards with comparatively large holes are equally known wherein some sound-absorbing material such as glass or rock wool is disposed behind the plates or, in the case of a ceiling facing, placed on top. The fraction of the area of the holes amounts, as a rule, to approximately 30 to 90% even though it may be less and even become as low as 10%. Drilling micro-perforated holes in thick plates of 6 to 30 mm, for instance, is too expensive and the small holesxe2x80x94roughly 1 mm in sizexe2x80x94would xe2x80x9cheal upxe2x80x9d again in wood boards or gypsum plaster boards because the wood fibres would extend into the interior of the hole and, in gypsum plaster boards, the fine gypsum would clog the holes.
The present invention is therefore based on the problem of providing a constructional element, which permits a low-cost utilization of the micro-perforation with application of a thick plate.
This problem is solved in accordance with the invention by the plate-shaped constructional element according to claim 1. Expedient embodiments of this constructional element are characterized in the dependent claims.
The issue of the present invention is the realization of a micro-perforation in comparatively thick plates or boards (approximately 6 to 30 mm thick) made of wood, synthetic material or gypsum plaster board, which absorb sound either as panels or cassettes of the type of a wall wainscoting or as suspended ceiling or even as jointless facing shell or part of a posted wall having a dual-shell structure.